1. Cell Membrane & Passive Transport:
EQ: What are the basic parts of cell membranes, and what is the job of each part? Can I diagram diffusion of oxygen, facilitated diffusion of glucose, and osmosis across a cell membrane?

2. BOUNDARY OF THE CELL: Cell Membrane Diagram:
Cell: smallest unit that can carry out all the activities for life. (the “atom” of biology)
Cell Membrane Diagram:
Outside of cell
Inside of cell (cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains

3. Membrane Descriptives:
Semi-Permeable—certain molecules can pass through the membrane, but not all molecules can
Fluid Mosaic Model—Proteins “float” in a fluid or moveable layer of phospholipids

4. Components of the Cell Membrane
***Reference the image on slide #2***
Phospholipid bilayer—
phospholipids have a phosphate head (yellow circle)
lipid tails (the brown tails).
The phosphate heads line up on the outside because they are hydrophilic (water-loving).
The lipid tails line up on the inside because they are hydrophobic (water-hating).
Proteins—act as channels or pumps to help molecules pass through the membrane
Carbohydrate chains—help cells recognize and communicate with each other

5. Solution terms: we discussed this during basic chemistry notes…
Solution – mixture of solute and solvent
(Ex. Kool-Aid = powder + water)
Solute – substance being dissolved (ex. Kool-Aid powder, Salt, or sugar)
Solvent – substance dissolving solute (ex. Water, which is a universal Solvent)

6. Membrane traffic
Passive transport~ diffusion of a substance across a biological membrane (NO ENERGY needed)
Ex. 1 Diffusion~ the overall movement of particles from a region of high concentration
to an area of low concentration
Ex. 2 Osmosis~ the diffusion of water across a selectively permeable membrane

7. Concentration: the relative amount of a given substance contained within a solution or in a particular volume of space; the amount of solute per unit volume of solution.

8. Results of Diffusion Dynamic equilibrium
Once diffusion has evenly distributed the solute throughout the solvent, movement of particles continues with no change in concentration
Homeostasis
Preservation of equilibrium

9. Diffusion depends on concentration gradient:
Concentration gradient: the difference in concentration of a substance across space
Diffusion is said to move down a concentration gradient
Diffusion continues until there is NO concentration gradient
Ex: O2 diffuses into oxygen depleted blood

10. Diffusion Rules:
Small Molecules like WATER, OXYGEN, AND CARBON DIOXIDE CAN MOVE in and out freely.
Large molecules like PROTEINS AND CARBOHYDRATES CANNOT
Charged IONS CANNOT

11. Osmosis~ the diffusion of water across a selectively permeable membrane.
Water likes to DILUTE high concentrations of solute

12. Osmosis in the Real World
Bryophytes, or mosses, are plants that depend on osmosis transfer water from the environment into the plant.
Bryophytes can never grow tall, because they cannot pull the water against gravity just using the concentration gradient.
Bryophytes must also live in wet environments

13. Review: Osmosis is the diffusion of _______ across a cell membrane.
Osmosis and Diffusion are both types of __________ transport.
Passive transport does or does not require energy?
Small molecules can not move across freely. T or F
Large molecules can move freely. T or F

14. Three Different Types of Solutions
Isotonic Solution
Hypotonic Solution
Hypertonic Solution

15. Isotonic Solution
The solute outside the cell is equal in concentration to the solute in the cell.
The cell retains its shape.
water moves equally in both directions (into and out of the cell)
Normal looking cells

16. Hypotonic Solutions
Solution outside the blood cell contains a lower concentration of solute than inside of the cell.
Water will diffuse inside the cell.
cell will lyse (burst).
In Animal cells - cytolysis.
Plant cells do not burst- turgur pressure— grocers use this idea

17. Cells in a Hypotonic Solution

18. Hypertonic Solutions
The solution outside the cell has a higher concentration of solute than inside of the cell.
Water will diffuse out of the cell,
causing the cell to shrink
or crenate
Why should you not salt meat before cooking?
CRENATION PLASMOLYSIS

19. Cells in a Hypertonic Solution

20. In what type of solution would these cells be found?

21. Water Balance Summary Osmoregulation~ control of water balance
Hypertonic~ higher concentration of solutes
Hypotonic~ lower concentration of solutes
Isotonic~ equal concentrations of solutes

22. Plasmolysis Turgidity in plant cells.

23. What type of solution is this?
Hypertonic
What will happen to the cell?
It will shrink.